Probes having sensors are known, but in the past once the sensor dies, in particular when a fluid reservoir of an electrode type sensor is spent, the entire probe was discarded. That may not have been too expensive prior to “smart probes,” but now that probes, like those disclosed herein, carry an on-board circuit board with memory and numerous other functionalities, it is expensive to just throw away the entire probe.
To solve this problem and address this long-felt need, Applicants developed a replaceable probe head that allows the body of the probe housing the more expensive circuit board and/or other electronics to be reused. In the embodiments disclosed herein, only the probe head is discarded. The probe head and probe body when connected to one another define a probe for sensing parameters of an environment. In particular, the probes are intended for use underwater, even to depths of 300-400 meters. The probe's housing is preferably watertight to protect the circuitry connected to the sensor.
Since the replaceable probe head is removeably connectable to the probe body, the potential for water to have access to the connection between the two is increased. It was observed that when water was present at the probe head to probe body connection that the current flow between the replaceable probe head and the probe body experience low impedance, which created detrimental shifts in the sensor readings. Applicants have found that the addition of an operational amplifier within the probe head between the working electrode and the electrical connector successfully electrically isolates the high impedance signals in the probe head from the low impedance interconnect and provides stable sensor readings to the circuit board in the probe body.